Diversity of the Vascular Epiphyte Flora at Two Different Elevations

F. Miranda-Aviles1,2 & P.M. Jørgensen2 1 Herbario Nacional de Bolivia, Instituto de Ecología, Universidad Mayor de San Andrés, Casilla 10077, La Paz, Bolivia [email protected], [email protected] 2 Missouri Botanical Garden, P.O. Box 299, St. Louis, MO 63166-0299, USA

Introduction The montane forests are very diverse; here the epiphytes represent a large proportion of the diversity of plants1. Under favorable conditions epiphytes may reach 25% of the species found in a hectare2. The placement of epiphytes is typically divided in five different zones3 on a tree. The composition and life-form change among the zones. The most important epiphyte vascular plant 4 5 6 families are Orchidaceae , ferns , Bromeliaceae, and Araceae . Stelis purpurea Oncidium scansor Elleanthus capitatus Inventories of epiphytes are few and at very different scale and are therefore difficult to compare. In the Bolivian Yungas 637 epiphytes Percentage of species at the study sites 1 have been recorded . A total of 175 epiphyte species were found in 35 0.32 ha in the forest of Cotapata7, and 147 species were found in Pauje Yuyo foothills of the Madidi National Park8. 30 Wayrapata Methods 25

In this study we made two inventories 1) at Pauje Yuyo between 20 900–1050 m and 2) at Wayrapata between 1290–1470 m. Both % localities are found near the border between the provinces Franz 15 Tamayo and Bautista Saavedra in the Integrated Management 10 Area Apolobamba in the Department of La Paz (Fig. 1). 5 We inventoried all epiphytes and hemiepiphytes in the understory in 10 plots each 400 m2, five at each site and located at different 0 elevations. In each plots we also inventoried the largest and most Orchidac Ferns Araceae Bromel Piperac Others epiphyte covered tree completely8. The position of the epiphyte was classified following Johansson3 (Fig. 2). The elevational range (930–1470 m) here studied is very poorly known. There are few floristic studies and even fewer studies that Pauje Yuyo focuses on epiphytes10. Despite differences in methodology we fell comfortable concluding that the diversity we find is relatively high compared to other studies11. However, we find fewer epiphyte species than Ibisch2 did in a smaller area, but we find approximately half the number of species found by Webster & Rhode12 in an area 110,000 times larger.

Wayrapata

Fig. 1. Study site The relative patterns of diversity of families is similar in the lower 3 Fig. 2. Johansson zones four Johansson zones. Araceae diminishes in diversity with an increasing zone class, ferns are relative constant independent of The upper crow or V the zone, while orchids becomes more diverse as the zone class terminal barnches increases. For class five there is a change in pattern, here the The middle of the crown Bromeliaceae are more diverse at Pauje Yuyo while the ferns are IV or secondary branches more diverse in Wayrapata. This difference in relative composition may be caused by an increased in dryness (Bromeliaceae better The lower crown or III adapted to a dry season than ferns) at the Pauje Yuyo versus the primary branches Wayrapata locality, this correspond also to the total diversity as epiphytes richness is predicted to follow high humidity areas. II Upper part of trunk The distribution of epiphytes in the Johansson zones found in this study compares well with other works2, 3, 7, 12. The zones that I Basal 1 m of the trunk contain the highest diversity are 2, 3, and 4. Araceae is well represented in zone 1 and 27. Bromeliaceae represent 70% of the species in zone 5 at Pauje Yuyo. Orchids are present in all zones Results but there is a clear differentiation in size, only smaller orchids are We recorded 127 species at Pauje Yuyo contained in 54 genera present in zone 5. and 24 families, at Wayrapata we found 201 species in 61 genera Literature cited and 25 families. The beta-diversity compared across sites was 1 Ibisch, P. & S.G. Beck. 2003. FAN, Santa Cruz de la Sierra, Bolivia large with only 48 species in common, and at the same time the 2 Ibisch, P. 1996. Arch. Naturwiss. Diss. 1: 1–357 3 Johansson, D.R. 1974. Acta Phytogeogr. Suec. 59: 1–129. alpha-diversity increases with increasing elevation, in the 4 Vasquez, R. & P. Ibisch 2000. FAN. Santa Cruz de la Sierra, Bolivia, 550 pp. elevational range studied, which coincides with Gentry & Dodson9. 5 Kessler, M. 2001. Biodivers. & Conservation. 10: 1897–1920. 6 Krömer, T. & R. Gradstein. 2003. Selbyana 24(2): 195. 7 Acebey, A. & T. Krömer. 2001. Revista. Soc. Stud. Bot. 3(1/2): 104. 8 Gentry A.H. & C. Dodson. 1987. Ann. Missouri Bot. Gard. 74: 205–233. 9 Krömer T., M. Kessler, S.R. Gradstein & A. Acebey. 2005. J. Biogeogr. 32(10): 1799– 1809. 10 Küper, W., H. Kreft, J. Nieder, N. Köster & W. Barthlott. 2004. J. Biogeogr. 31: 1477–1487. 11 Webster, G.L. & R.M. Rhode. 2001. Univ. Calif. Publ. Bot. 12 Nieder J., S. Engwald & W. Barthlott. 1999. Selbyana 20(1): 66-75.